Today, it is important in many applications to detect the unauthorized opening of a door or a window. For example, alarm systems for buildings may include intrusion detectors which are situated on individual doors and windows of a building and are used to detect the opening of the door or the window.
If the alarm system is armed, it may trigger an alarm in the event of an unauthorized opening of a door or a window of the building and transmit an alarm signal, for example, to a central reporting center or to the police.
The detection of an unauthorized opening of a door or a window of a building, i.e., an intrusion via the door or the window, is carried out, for example, via a sensor which is configured to detect vibrations or jarring occurring at the door or the window due to the intrusion.
Patent document DE602004011587T2 discusses a conventional intrusion sensor for monitoring a building.
This jarring may, for example, be caused by the break-in tool used on the door lock or the window, for example, a skeleton key or other lock-picking instruments. However, this jarring may also, for example, be caused by the exertion of brute force on the door for separating the door lock from the corresponding receptacle situated in the door frame. This is the case, for example, when kicking in the door.
In this case, the sensor is generally secured to the inside of the door or the window, i.e., to the inside of the building. The sensor generally simultaneously detects accelerations in all three spatial axes and reports them to the alarm system or to a microcontroller integrated into the sensor which transmits an intrusion signal to the alarm system.
If a sensor which is attached to the inside of the door or the window only monitors motion in the three spatial axes, false alarms may be triggered very easily, since the sensor is not able to detect the actual reason for the jarring.
For example, if a child on the floor inside the dwelling bumps into a door which is equipped with a sensor as described above, it is not possible to rule out the sensor triggering an intrusion alarm, although no intrusion is occurring. Since the sensor only detects the jarring of the door, it cannot differentiate whether the door was jarred by an authorized person or an unauthorized person.